The invention relates to an apparatus for loading and unloading a process chamber of a coating device with at least one substrate by means of a gripper and an automated handling unit.
It is known for the substrates which are to be coated to be introduced into the process chamber of a coating device and removed from it again by means of a gripper of an automated handling unit. A CVD process can be carried out in the process chamber. The gripper can act on the substrate directly. By way of example, the gripper may form a tongue which engages beneath the substrate. To unload the apparatus, this tongue has to be moved under the substrate. A gripper of this type can in each case only grip one substrate. Moreover, for the tongue to engage beneath the substrate, the substrate has to be lifted off its supporting surface slightly. For the substrate to be lifted off the substrate holder, the substrate holder has an apparatus, for example in the form of pins, which move out of the substrate surface in order to lift the substrate. An arrangement of this type leads to an inhomogeneity in the supporting surface for the substrate and therefore to undesirable inhomogeneous temperatures on the substrate holder surface or over the substrate. Other methods for temporarily lifting the substrate which have been proposed in the prior art likewise have these drawbacks.
Furthermore, it has been proposed in the prior art to remove not just the individual substrates, but rather the substrates together with the substrate holders, from the process chamber.
Working on the basis of this prior art, the invention is based on the object of improving the loading and unloading of a process chamber with at least one substrate.
This object is achieved by the invention specified in the claims, among which in claim 1 it is provided firstly and substantially that the apparatus has a loading plate which can be gripped by the gripper and forms a supporting location, which is formed by an edge of an opening associated with each substrate, for each at least one substrate. The substrate is therefore located above the opening during loading. The edge of the opening supports the edge of the substrate. In a preferred configuration of the invention, the bottom of the opening is formed by a recess. The substrate is therefore located in a recess. The result of this is that acceleration forces applied to the loading plate cannot displace the substrate out of the supporting location. The opening associated with each substrate may be circular, so that only the edge of the substrate rests on the edge of the opening. The contour of the opening is preferably similar to the peripheral contour of the substrate. If the substrate is substantially circular in form, the opening is likewise circular in form, but with a smaller diameter. If the substrate has a rectangular or polygonal peripheral contour, the opening preferably has the same peripheral contour, but with a smaller diameter. The loading plate per se may have a multiplicity of supporting locations and may have a substantially circular circumferential contour. The supporting plate may have an annular collar on the rear side. The substrate holder may have one or more pedestal-like substrate carriers, on each of which a supporting plate can be placed in such a manner that surface portions of the substrate carrier are at a gap spacing from the substrate or that the substrate rests flat on a surface portion. In the former case, the heat transfer from the heated substrate holder to the substrate is effected by means of thermal radiation. In the latter case, the heat transfer is effected by heat conduction. The annular collar surrounds a receiving cavity for receiving the substrate holder. The substrate carrier may be an integral part of the substrate holder. However, it is preferable for the substrate carrier to be a plate driveable in rotation on a gas bearing. The supporting plate can be fitted onto this plate in such a manner that it rotates with the substrate carrier. The loading plate can be located in a depression in the substrate holder, in such a manner that its surface is flush with the surface of the substrate holder. The material of the loading plate and the material of the substrate holder may be identical or similar. The annular collar may have a conically running inner wall. The substrate carrier, onto which the loading plate can be placed, may form a circumferential formation of matching shape. When the loading plate is being placed on the substrate carrier, a self-centering action of the loading plate is then effected. The outer wall of the annular collar may have a circumferential groove. This circumferential groove may in turn form an annular engagement groove for a hook of the gripper to enter. The gripper may preferably have two gripper arms and a hook. The length of the two gripping arms may be shorter than the diameter of the loading plate, so that as a result of the eccentric engagement of the gripping arms in the circumferential groove of the loading plate a tilting moment is produced when the loading plate is lifted. This tilting moment causes the loading plate to tilt at the moment when it is lifted. As the loading plate tilts, the hook which has been introduced into the circumferential groove moves into the engagement groove in the periphery of the loading plate, so that the latter is securely held by the gripper. To ensure that the gripper, and in particular the arms and the hook, come into contact with the loading plate, the substrate holder has at least three depressions which are open toward the edge. One of these depressions forms a centering opening. This opening may have trapezoidal opening walls. A centering projection of the gripper, with which the hook is also associated, moves into this centering opening. As the centering projection moves into the centering opening, the rotatable substrate holder can be rotated slightly until it has reached its optimum orientation. This is of benefit to positionally accurate placing of the loading plate on the substrate carrier. Two passage-like cut-outs, which are open toward the edge of the substrate holder, are used for engagement of the gripping arms of the gripper during loading and/or unloading of the process chamber with the loading plate. The apparatus may also have an associated removal device. This removal device has vertical supports associated with each opening in the loading plate. The plate can be fitted over these vertical supports. In the process, the vertical supports penetrate through the openings in the loading plates and thereby lift the substrates off the loading plate. The substrates are then located on the vertical supports and can be collected by the same or a different gripper in order to be fed to a cassette or other intermediate loader. The vertical supports may be formed by at least three vertical pins.
The configuration described above provides an automatic loading and unloading system for one or more substrates for a coating device. The loading and/or unloading may take place within a very short time. The operation can take place at process temperatures (400° C. to 1200° C.). This minimizes the times between the actual coating operations. The substrates are removed from cassettes, which can hold a plurality of substrates, and transported into the reactor. After coating has taken place, the substrates are put back in the cassettes. During loading into and unloading from the process chamber, the substrates are not gripped or clamped either on their surface or at their peripheral edges. In particular, there is no contact with the surface of the substrate at any time. The entire operation can take place automatically. A further advantage is that no particles are generated or transported to the substrate surface during loading and unloading.
To load the process chamber with a plurality of substrates, these substrates are first of all, outside the chamber, automatically placed in recesses in a thin loading plate which consists of an identical or similar material to the substrate holder in the chamber. This loading plate is formed in such a way that only the external periphery of the substrates is located in a cut-out in this plate. The bases of these cut-outs form openings, the diameters of which are only slightly smaller than the substrate diameters. This loading plate can be loaded by means of the removal device. For this purpose, the releasable loading plate is first of all fitted over the vertical supports. Then, at least one substrate is placed onto the vertical supports in an accurately positioned manner by means of a robot arm. Then, the loading plate is displaced vertically upward until the substrates are resting on the edge of the openings. Unloading is carried out in the reverse order. The loading plate is then introduced into the process chamber by the gripper. As the centering projection described above moves into the centering opening in the substrate holder, the substrate holder is positioned by means of the centering projection, so that the loading plate can be fitted accurately over the substrate carrier. The substrate carrier may be hotter than the loading plate. Then, however, heat transfer causes the loading plate to be heated up to the temperature of the substrate holder, with length expansion taking place in such a manner that the diameter of the loading plate is increased slightly. On account of the conicity of the inner wall of the annular collar and of the circumferential wall, which is of matching shape, of the substrate carrier, as it heats up the loading plate slips downward into its final position, in which the substrates either rest flat on portions of the substrate carrier or are at a defined gap spacing from the surface of the substrate holder. The gap spacing is defined by the material thickness of the loading plate, which rests flat on the surface of the substrate carrier.
On account of the centering projection, which interacts with the centering opening in the substrate holder, the rotationally driven substrate holder only has to be roughly pre-positioned for loading and unloading. Precision positioning is effected by the gripper itself. The retaining of the loading plate on the gripper is effected when the plate is tilted as it is lifted, with a hook engaging in an annular engagement groove in the loading plate. The substantially rotationally symmetrical circumferential contour of the loading plate makes it possible for the latter to be gripped by the gripper independently of its rotational position.